Carbon pile rheostat



Dec. 26, 1950 E. P. TURNER 2,536,012

CARBON PILE RHEOSTAT Filed April 1, 1949 3 sheets-sheet 2 Z9 .ZNVENTRWRNW Dec. 26, 195@ E. P. TURNER 25361)@ CARBON PILE RHEOSTAT Filed Aprill, 1949 3 Sheets-Shave?l 5 INVENTR ATTORNEY Patented Dec. 26, 1950PATENT OFF-ICE Y Claims.

Thisainventioniirelatesitoi:oarbonipilefrheostats f orcontrollers andmore. particularly; ton carbon pile -,rheostats f used to control lthe'starting, .stop pingsl and: speedYI of! a..y sewingtt'machinexelectricmoton:

Onefof "the obj erts of thislirlventionr` is torpro.- videfaf singlefcarbon pilerrheostat :which conrpact,L easily assembledi and.which;allows .the` ope erating.` button to .be actuated.over.. aawidevrange at -a'zcons'tant pressure and therebyfvary the ree sistance ofthe. carbonipile*A at auniformiL ratio.

Another object 1 ofi: this invention is' thefprovisionzotV a:thinzmeta'l "supportiforg themarbonzpile,

which supportisA insulatedzirom. the"l carbon pile and: is formed with*ilaterally projecting heat dissipating ns for the purpose or.: conductingheataway from theipila Another; objectofi thisainvention. is'.A the`pro.- visiorn of ai toggleaspring :actuator lwhich has the quintuple;function of'fopposi-ng'. movement of the pressureebutton; conducts; theelectrical current; acts'. as azswitch for turning-the electricalcurrentfonzand off: appliesxpressure tottheecarbon pile andshort-circuits. the: carbompileg tofobtain fullispeed offthe motor;l

With the above and otherfobjects-.inlviewas will hereinafter.' appear;the invention comprises thevv devices, combinations: and arrangements ofparts hereinafter set*- forth: and illustratedy inthe accompanyingdrawings ofa preferredembodiment of" the" invention, from whichy theseveral features .of the inventionz'andY the. advantages; attained.thereby will be readily understoodby those skilled in' the art.

Inthe drawings:.

Fig. lista; top planrvievv-of azsinglepileoarbon` .controllers embodyingtheeV invention', the;y coverandtpush button.. being g removed. to;expose; the parts-beneath.

Fig: 2 is. alongitudinal section :taken .substantially alongl thee line2 2v of L thecontroller shown inFig. LWthzthe cover-plateappliedthereto;

, Figs; Brand: i are? transversefvertical. sections taken :along lthe.line 3--3 and 4 4, respectively, ,OFgwZi- Figi'. 5 bottom planview. ofthewrem'ovable cover for the controller.

6,-isfa top'planview similarftofFig. 1, the spring actuator forlcompressingv the carbon pile being-.removed= tofexposefthe partsbeneath.

Fig. 'lis atoplplanview ofthefmetalsupport for the ,carbon-pile..

Fig. 8 is an endl elevation on the.v controller as shownin Fig. 1.

Fig..9.is a `top planv4 viewof4 asinglepile carbon contrpllerA similar.to.. thatishownf. in. Fig... l with 21- azmodiiied form of` mechanismfor compressing the carbon pile.

Fig.y lO'isal longitudinal sectional view'taken substantially along theline Ill-of Fig. 9'.

Figgll isatransverse sectional view taken substantiallyA along the lineI IJ-I Iof Fig. 9.

In thev embodiment of this invention shown inLFigs. 1 to 8, inclusive,the improvedcontroller comprises' a hollowcasingformed byarectangularly-fshaped and'substantially liat base I9, anda..rectangularly shaped top or cover II, each beving-.preferably mouldedin-one-piece'vfrom phenolic condensation material or'artiiieial resin.The parts: Ill/and` II are detachably secured-together by means ofcorner screws I3 which are screwed in. corner, lugs. I4 formed on thetopy I I. The screws I3 also function to hold the rubber feetlzin'position onthe corners ofthe base i0.

Carried by the baseA IIJ.L is asubstantially rectangularlyshapedrsheet-metal member, indicated generall'yas I S (Figs. l andv 7),formed in one pieceandihaving a tubularv longitudinal central .portion I'I f which `.en'lbraces and supports al single carbon disk pile I8; Thesheet metalv member alsoghas'oppositely directed legror. heatdissipating iinzportions I9 and, 2l! Whichare securedto .the base I0bythe screws 2-I. This member IG is. coated-withal' dielectric porcelainenamel so asl to.electricallyinsulate thezcarbon' pile from Vitssupport. The advantage ofthe above described support. for thecarbon-pile is that theA sheet metalmember Ilirapidly conductsheatgenerated inthe. carbon pileaway from the pile/and spreads itA over;a large areathus preventing concentration ofitheheat in the pile..

Formed ori-the insulatingbase la is'anupstandf ling lug 231 havingagroove-24 (Figs. 1 and 2) `formed inits upper face. A: T-shapedcompres-.- sion plunger' 23 is slidably fitted in the groove 24-` andextends through a cap 25.- at one endA of the pile. Theenlargedv endy2'!Y of -tbe'plunger 2S islocated within. the cylindricall portion I'Iof the sheet metal member I6 and in contact with the .carbon pile I8.

Atthe other end of the pile,. the base. It) is formed witntwospacedupstanding lugs 28 each of which is providedwith a vertical slot 29(Figs. 1 and 4) thereby providing conlining shoulders for anut 3b.Threaded. inthe nut is a screWf3I havingfoneof` its endsextendingthroughthe cap 32 and:- into engagement with they carbon pile. Thevother end ofthe screw Sl: is formed with a screw driver slotso that' it may beadjusted longitudinally of thepile for the purpose `of-V varying theinitial pressure on the pile.

Y Located ,at one vside of: and parallel. tothe .car-

bon pile I8 is a resilient copper conductor strip 33 which is secured tothe base Il] by means of a screw 34 (Figs. 3 and 6). A flexibleelectrical conductor 35 is electrically connected to the strip 33.Formed on the strip 33 is a laterally extending portion 33 (Figs. l and6) which is electrically connected to the adjustable screw 3 I. On theopposite side of the carbon pile, a resilient copper conducting strip 3lis secured to the base I by a screw 38 vand is electrically connected toa flexible electrical conductor 39.

The tops of the lugs 28 are slotted to receive a pivot-pin 40 formedwith a reduced portion near each end. In order to provide means forvarying the pressure on the carbon pile there is provided a U-shapedspring or resilient metal member having limbs 42, 42', the free ends ofwhich are bent back upon themselves to encircle and embrace the reducedportions of the pivot pin 40 anchored in the slots formed in the tops ofthe lugs 28. The connecting portion 43 of the U- shaped member lies in anotch 44 formed in the endwise movable plunger 26.

For the purpose of bending or flexing the U- shaped spring centrally ofits length to cause it to act as a toggle joint and apply pressure onthe carbon pile |18 there is slidably mounted in the cover or top I I amanually operable push button or pedal 45. The pedal 45 has twodepending guides 46 which are slidably received in guiderways 4'I formedin the top I l and two depending lugs 48 which straddle the carbon pileand rest upon the limbs 42, 42 of the U-shaped actuating spring.

In the operation of the above described motor controller or rheostat,when the pedal 45 is depressed by the operator the downward movement ofthe pedal causes the lugs 48 to flex the limbs 42, 42' of the U-shapedspring downwardly and the initial downward movement of the limb 42' 4Figs. 9 to 11, inclusive, the rheostat is not actuated by a foot pedalbut is adapted to be mounted on the sewing machine or similar cabinet ina substantially Vertical position and operated by a pull rod having oneend connected to a treadle and its other end connected to thecontroller. In this modification, the casing comprises a base A andremovable cover B forming a housing for a carbon pile compression unitwhich is identical with that shown in the preceding figures. Thediierence in the two constructions resides in the substitution for thepush-pedal 45 of a pullblock 50 slidably mounted in suitable guidewaysformed in the casing. The pull block 50 is molded from phenolicthermosetting material with a metal insert pull plate 5I which isadapted to be connected to a pull rod. Connected to the pull block 50 bythe nut andbolt 52, 53, (Fig. 10) are two L-shaped arms 54 which havetheir free ends pivoted at 55 t0 the depending limbs of bell-cranklevers 62 located on opposite sides of the carbon pile I8 and pivoted at56 to the upstanding arms 51 of a U-shaped bracket 58 which is securedto the base A by the screws 59. Springs 5U each having one of their endsconnected to the L- shaped arms 54 and their other end connected to anupstanding lug 6I formed on the bracket 58 serve to yieldingly maintainthe above described parts in the position shown. Pivoted to causes thelimb 42 to engage the resilient conducting strip 3'I and the circuit isthereby closed through the carbon pile resistor I8.

The circuit at this time is as follows: From the lead 39 through theconductor strip 3'I and U- shaped metal spring to the metal plunger 26,through the plunger 26 and carbon pile I8 to the screw 3I, thencethrough the laterally extending portion 33 of the strip 33 to the lead35.

It will be observed that further downward movement of the pedal causesfurther flexing of the limbs 42, 42 of the U-shaped spring and as oneend of the spring is anchored by the pivot pin 40 the plunger 26 isforced against the carbon pile thereby compressing it. It will beunderstood that the limbs 42, 42 are, in eiect, toggle joints whichallow the operating button or pedal 45 to be actuated over a Wide rangeat a constant pressure to thereby vary the resistance of the carbon pileat a uniform ratio.

Continued downward movement of the pedal 45 causes the limbs 42, 42' tobe further ilexed thereby gradually increasing the pressure exerted onthe carbon pile until the pressure is at a maximum and the electricalresistance oered by the pile is at its minimum. At this point the limb42 engages the spring conductor strip 33 which lies relatively close tothe base I0, as shown in dotted lines in Fig. 2. When the limb 42engages the other arm of the bell-crank lever 62 at'63 is a member 64which connects the arms of the bellcrank levers and extends over thecarbon pile I8. The member 64 is formed with shoes 65 which centrallyengage the limbs 42 and 42 of the U- shaped spring. Y

From the above it will be understood that when the pull-block 5B ismoved to the left as viewed in Figs. 9 and l0 the arms 54 will swing thebellcrank lever 62 about its pivot 56 thereby causing the shoes 65 toilex the limbs 42, 42 of the U- shaped spring in the same manner and forthe same purpose as the lugs 48 of the pedal member 45 when the latteris depressed.

Having thus set forth the nature of the invention, what I claim hereinis:

l. A controller for electric motors comprising a base, a carbon pileresistor carried by said base, a U-shaped spring having its limbsarranged parallel to said carbon pile, means for anchoring the free endsof said limbs, and manually controlled mechanism for engaging andsimultaneously flexing each of said limbs intermediate their ends forthe purpose of varying the pressure applied to the carbon pile resistor.

2. A carbon disk resistor for electric motors comprising a base, a sheetmetal support carried by said base and having a coating of insulatingmaterial on its outer surface, a carbon pile carried by said support, aU-shaped spring for applying pressure to said carbon pile, manuallycontrolled mechanism for engaging and simultaneously iiexing the limbsof the U-shaped spring, and a flexible electrical conductor locatedbeneath one of the limbs and adapted for engagement said heath each limband arranged so that when the limbs are initially flexed one of saidstrips is engaged by'one of the limbs to connect the carbon pile inseries in the circuit and when the limbs are completely flexed the otherstrip is engaged to short circuit the carbon pile.

4. A controller for electric motors comprising a base, a sheet metalcarbon pile support coated with electrical insulating material securedto said base, said support being formed with a longitudinal tubularportion and oppositely directed heat dissipating fins extendinglaterally from said tubular portion, a carbon pile carried by thetubular portion of said support, a plunger extending into said tubularportion and in contact With one end of said carbon pile, a U-sliapedspring having its limbs located on opposite sides of said carbon pileand its connecting portion in engagement with said plunger, andmechanism for applying pressure to the limbs of said U- shaped spring toshift said plunger relative to said carbon pile for the purpose ofapplying pressure to said carbon pile.

5. A controller for electric motors comprising a base, a sheet metalcarbon pile support coated with electrical insulating material securedto said base, said support being formed with a longitudinal tubularportion and oppositely directed heat dissipating fins extendinglaterally from said tubular portion, a carbon pile carried by thetubular portion of said support, a plunger extending into said tubularportion and in contact with one end of said carbon pile, a ilat springanchored to said base and having resilient limb portions, and mechanismfor applying pressure to each of said limb portions transverse to theirlength and intermediate their ends to cause said plunger to apply agradually varying pressure to said carbon pile over a, Wide workingrange of said mechanism.

6. A controller for electric motors comprising, a support, a carbon pileresistor carried by said support, a compression plunger located in oneend of said carbon pile, a U-shaped spring having its limbs located onopposite sides of said carbon pile and its connecting portionoperatively connected to said compression plunger, means for -anchoringthe free ends of the limbs of said U-shaped spring to said support atpoints adjacent the other end of said carbon pile, and manually operablemeans for simultaneously flexing both limbs of said U-shaped spring toshift said plunger relative to said carbon pile for the purpose ofapplying pressure on said carbon pile.

7. In a controller for electric motors having a support and a resistorsecured to said support, the improvement which consists in varying thepressure upon said resistor over a wide range by means of a springhaving limbs located on opposite sides of said resistor and arrangedsubstantially parallel thereto, one end of each of said limbs beinganchored adjacent one end of said resistor and the other end of thelimbs being connected to apply pressure to the other end of theresistor, and manually operable mechanism for flexing said limbssimultaneously at points intermediate their ends to produce a toggleaction and thereby vary the resistance of the carbon pile at asubstantially uniform ratio.

EDGAR P. TURNER.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,460,815 Hynes July 3, 19231,581,957 Keller Apr. 20, 1926 2,371,772 Naul Mar. 20, 1945

